The purpose of this project is to determine whether serum biactive luteinizing hormone (Bl-LH) levels more closely correlate with the status of puberty than do serum immunoreactive LH (I-LH) levels and whether there is a qualitative change in LH during puberty. Although it is well documented that mean serum LH titers increase significantly during puberty, previous methods including bioassay of LH in urine and blood have not been sensitive enough to regularly distinguish prepubertal from pubertal or adult levels of LH in individuals with normal pubertal development. Likewise, although the mean I-LH response to a strand bolus of luteotropic releasing hormone (LRH)-stimulated LH changes through pubertal maturation, it does not necessarily characterize the pubertal stage of any one individual. We have recent evidence in our laboratory that the I-LH response to an infusion of LRH may improve this distinction, perhaps by stimulating release of a "stored" pool of pituitary LH that is not release by a bolus of LRH. It is established that the bioactivity of LH is not always equivalent to its immunoactivity. The ration of B-LH to I-LH (B/I) expresses qualititive variations of the serum LH. We have recently demonstrated the qualititive changes in LH in agonadal girls treated with estrogen by showing that the B/I LH falls with time and amount of astrogen treatment. We plan to study the relationship of B-LH to I-LH in normal children followed longitudinally through puberty and in children and adults with abnormalities of puberty. B-LH and I-LH will be studied in serum samples obtained during both the basal state and in response to LRH stimulation. B-LH will be measured using testosterone production from isolated rat interstitial cells (RICT) as a highly sensitive bioassay for serum LH and I-LH will be measured by a standard radioimmunoassay. This proposal will test the hypotheses that 1) B-LH is a more sensitive indicator of the stages of puberty than I-LH and 2) that the quality of LH, as measured by B/I, changes pubertal maturation.